CLINICAL APPROACH TO ACID-BASE DISORDERS Metin Kapan, M.D. Professor of General Surgery Cerrahpasa School of Medicine Department of General Surgery Division of Hepatopancreatobiliary Surgery

CASE #1

A 22-year-old woman was brought to the emergency department with complaints of dizziness, fatigue, frequent urination and increased sensation of thirst.

CASE #1

PHYSICAL EXAMINATION • The patient was lethargic • Skin turgor was decreased • Blood pressure: 90/60 mm Hg • Pulse rate: 110/min • Respiration rate: 28/min • Temperature: 370C

Any comments about the diagnosis ?

CASE #1

LABORATORY FINDINGS Glucose: 420 mg/dl BUN: 30 mg/dl Creatinine: 1.3 mg/dl Na: 130 mEq/L K: 5 mEq/L Cl: 98 mEq/L

Arterial Blood Gas PO2: 90 mm Hg PCO2: 20 mm Hg HCO3: 8 mEq/L pH: 7.22

What is the acid-base disorder ?

pH = - log [H+] [H+] in arterial blood = 35-45 nEq/L

Hidrogen ion concentration is one millionth of other electrolytes

pH = - log [H+] -log [35x10-9] = 7.45 -log [40x10-9] = 7.40 -log [45x10-9] = 7.35

Eq/L

pH = 7.35 – 7.45

Henderson Equation PCO2 [H = K [HCO3]

[H+]

Henderson Equation PCO2 [H = K [HCO3]

[H+]

ARTERIAL BLOOD [H+] = 35 – 45 nEq/L pH = 7.35 – 7.45 PCO2 = 35 – 45 mm Hg [HCO3-]= 22-26 mEq/L

CASE #1

LABORATORY FINDINGS Glucose: 420 mg/dl BUN: 30 mg/dl Creatinine: 1.3 mg/dl Na: 130 mEq/L K: 5 mEq/L Cl: 98 mEq/L

Arterial Blood Gas PO2: 90 mm Hg PCO2: 20 mm Hg HCO3: 8 mEq/L pH: 7.22

Can we interprete the acid-base status by the venous blood gas ?

7.35

7.45

ACIDEMIA NORMAL

ALKALEMIA

Metabolic Acidosis

Metabolic Alkalosis

Respiratory Acidosis

Respiratory Alkalosis

Kimyasal Tampon Sistemi Ekstraselüler alanda etkisini gösteren tamponlar (1) H2CO3/HCO3-, (2) NaH2PO4/Na2HPO4, (3) Protein H+/proteinat ve (4) Organik asitler/organik asit tuzları.

İntraselüler alanda etkisini gösteren tamponlar: (1) Böbrek tubulus hücresi ve eritrositlerdeki NaH2PO4/Na2HPO4 sistemi, (2) Dokulardaki protein tampon sistemi ve (3) Eritrositlerdeki hemoglobin H+/hemoglobinat tampon sistemi.

SIMPLE ACID-BASE DISORDERS [H+]

PCO2 =K [HCO3]

Metabolic Acidosis

pH Ø

SIMPLE ACID-BASE DISORDERS [H+]

PCO2 =K [HCO3]

Metabolic Acidosis

pH Ø

[H+]

PCO2 =K [HCO3]

Metabolic Alkalosis

pH ×

SIMPLE ACID-BASE DISORDERS [H+]

PCO2 =K [HCO3]

Acute Respiratory Acidosis

pH Ø

SIMPLE ACID-BASE DISORDERS PCO2 =K [HCO3] PCO2 + [H ] = K [HCO3] [H+]

Acute Respiratory Acidosis

pH Ø

Chronic Respiratory Acidosis

pH Ø

SIMPLE ACID-BASE DISORDERS PCO2 =K [HCO3] PCO2 + [H ] = K [HCO3] [H+]

[H+]

PCO2 =K [HCO3]

Acute Respiratory Acidosis

pH Ø

Chronic Respiratory Acidosis

pH Ø

Acute Respiratory Alkalosis

pH ×

SIMPLE ACID-BASE DISORDERS PCO2 =K [HCO3] PCO2 + [H ] = K [HCO3] [H+]

Acute Respiratory Acidosis

pH Ø

Chronic Respiratory Acidosis

pH Ø

[H+]

PCO2 =K [HCO3]

Acute Respiratory Alkalosis

pH ×

[H+]

PCO2 =K [HCO3]

Chronic Respiratory Alkalosis

pH ×/N

Compansatory response cannot bring the pH to normal limits

SIMPLE ACID-BASE DISORDERS Compansatory Primary Response Disturbance

pH

Metabolic acidosis

HCO3- ↓

PCO2 ↓

↓

Metabolic alkalosis

HCO3- ↑

PCO2 ↑

↑

Acute respiratory acidosis

PCO2 ↑

HCO3- →

↓

Chronic respiratory acidosis

PCO2 ↑

HCO3- ↑

↓

Acute respiratory alkalosis

PCO2 ↓

HCO3- →

↑

Chronic respiratory alkalosis

PCO2 ↓

HCO3- ↓

↑, N

CASE #1

LABORATORY FINDINGS Glucose: 420 mg/dl BUN: 30 mg/dl Creatinine: 1.3 mg/dl Na: 130 mEq/L K: 5 mEq/L Cl: 98 mEq/L

Arterial Blood Gas PO2: 90 mm Hg PCO2: 20 mm Hg HCO3: 8 mEq/L pH: 7.22

What is the acid-base disorder ?

CLINICAL APPROACH TO PATIENT WITH ACID-BASE DISORDER

History Physical Examination Laboratory Findings pH [HCO3] PCO2 Anion Gap

ELECTROLYTES IN DIFFERENT COMPARTMENTS Plasma (mEq/L)

Interstitial fluid (mEq/L)

Intracellular fluid (mEq/L)

142 4 5 2 153

144 4 2.5 1.5 152

14 140 4 35 193

104 25 2.3 0.94 15 5.76 153

114 30 2 1 0 5 152

2 8 40 20 55 68 193

Cations Na+ K+ Ca2+ Mg2+ TOTAL

Anions ClHCO3H2PO4-,HPO42SO42Proteins Org. anions TOTAL

AG 12

Anion Gap

HCO324

Na+ – (Cl- + HCO3-) = 12 + 2 mEq/L Na+ 140

Cl104

NORMAL ANION GAP (HYPERCHLOREMIC) METABOLIC ACIDOSIS AG 12

AG 12

HCO3-

HCO314

24

HCO3 loss

Na+ 140

Cl104

1. Urine 2. Stool

Cl114

HIGH ANION GAP METABOLIC ACIDOSIS AG 12

Lactate- - H+

HCO324

HCO314

Acid accumulation

Na+ 140

AG 22

Cl-

Cl-

104

104

CAUSES OF METABOLIC ACIDOSIS I. Normal Anion Gap (Hyperchloremic) Metabolic Acidosis 1. Gastointestinal loss of bicarbonate Diarrhea 2. Renal loss of bicarbonate Renal tubular acidosis II. High Anion Gap (Normochloremic) Metabolic Acidosis 1. Renal failure 2. Ketoacidosis 3. Lactic acidosis 4. İntoxications (salisylate, ethylene glycol, methanol)

CASE #1

LABORATORY FINDINGS Glucose: 420 mg/dl BUN: 30 mg/dl Creatinine: 1.3 mg/dl Na: 130 mEq/L K: 5 mEq/L Cl: 98 mEq/L

Arterial Blood Gas PO2: 90 mm Hg PCO2: 20 mm Hg v HCO3: 8 mEq/L v pH: 7.22 Acidemia

Anion Gap = 130 – (98 + 8) = 24 mEq/L High Anion Gap Metabolic Acidosis

COMPANSATORY RESPONSE IN METABOLIC ACIDOSIS

PCO2 = [(1.5 X HCO3-) + 8] + 2

CASE #1

LABORATORY FINDINGS Glucose: 420 mg/dl BUN: 30 mg/dl Creatinine: 1.3 mg/dl Na: 130 mEq/L K: 5 mEq/L Cl: 98 mEq/L

Arterial Blood Gas PO2: 90 mm Hg PCO2: 20 mm Hg v HCO3: 8 mEq/L v pH: 7.22 Acidemia

PCO2 = [(1.5 X HCO3-) + 8] + 2 PCO2 = [(1.5 X 8) + 8] = 20 mm Hg High Anion Gap Metabolic Acidosis

CASE #1

High Anion Gap Metabolic Acidosis (Diabetic ketoacidosis)

CASE #2

A 28-year-old woman was brought to the emergency department with complaints of persisting nausea and vomiting. She is pregnant at 10 weeks’ gestation

CASE #2

PHYSICAL EXAMINATION • The patient was lethargic • Skin turgor was decreased • Blood pressure: 95/60 mm Hg • Pulse rate: 120/min • Respiration rate: 12/min • Temperature: 36.40C

Any comments about the diagnosis ?

CASE #2

LABORATORY FINDINGS Glucose: 88 mg/dl BUN: 18 mg/dl Creatinine: 0.8 mg/dl Na: 136 mEq/L K: 3.0 mEq/L Cl: 96 mEq/L

Arterial Blood Gas PO2: 92 mm Hg PCO2: 36 mm Hg HCO3: 30 mEq/L pH: 7.54

What is the acid-base disorder ?

CASE #2

LABORATORY FINDINGS Glucose: 88 mg/dl BUN: 18 mg/dl Creatinine: 0.8 mg/dl Na: 136 mEq/L K: 3.0 mEq/L Cl: 96 mEq/L

Arterial Blood Gas PO2: 92 mm Hg PCO2: 36 mm Hg v HCO3: 30 mEq/L u pH: 7.54 Alkalemia

Anion Gap = 136 – (96 + 30) = 10 mEq/L

CAUSES OF METABOLIC ALKALOSIS I. Saline-Responsive Metabolic Alkalosis Vomiting, nasogastric suction Diuretic therapy: Loop diuretics, thiazides Posthypercapnia II. Saline-Resistant Metabolic Alkalosis Hypertensive Primary hyperaldosteronism, Cushing’s syndrome, renovascular hypertension, Liddle’s syndrome Normotensive Bartter’s syndrome, hypokalemia, hypomagnezemia

CAUSES OF ACUTE RESPIRATORY ACIDOSIS I. Inhibition of the medullary respiratory center Drugs: Opiates, anesthetics, sedatives Oxygen in chronic hypercapnia Cardiac arrest II. Disorders of the respiratory muscles and chest wall Myastenia gravis, periodic paralysis, Guillain-Barre syndrome, severe hypokalemia, severe hypophosphatemia III. Upper airway obstruction Laryngospasm, aspiration of foreign body IV. Disorders affecting gas exchange across the pulmonary capillary Adult respiratory distress syndrome, acute pulmonary edema, severe asthma or pneumonia, pneumothorax or hemothorax

CAUSES OF CHRONIC RESPIRATORY ACIDOSIS I. Inhibition of the medullary respiratory center Extreme obesity (Pickwickian syndrome) Sleep apnea II. Disorders of the respiaratory muscles and chest wall Spinal cord injury, poliomyelitis, amyotrophic lateral sclerosis, multiple sclerosis, kyphoscoliosis III. Disorders affecting gas exchange across the pulmonary capillary Chronic obstructive pulmonary disease

CAUSES OF ACUTE RESPIRATORY ALKALOSIS I. Psycogenic or voluntary hyperventilation II. Direct stimulation of the medullary respiratory center Neurologic disorders Septicemia Hepatic failure Salicylate intoxication III. Hypoxemia Pulmonary disease: Pneumonia, emboli, edema Congestive heart failure Hypotension or severe anemia IV. Mechanical ventilation

CAUSES OF CHRONIC RESPIRATORY ALKALOSIS I. Direct stimulation of the medullary respiratory center Neurologic disorders Pregnancy and the luteal phase of the menstrual cycle Chronic liver disease II. Hypoxemia Pulmonary disease: Interstitial fibrosis Congenital heart diseases Severe anemia High altitude residence III. Mechanical ventilation

COMPANSATION IN ACID-BASE DISORDERS METABOLIC ACIDOSIS PCO2 = [(1.5 X HCO3-) + 8] + 2 METABOLIC ALKALOSIS PCO2 increases 0.5-1 mm Hg for every 1 mEq/L increase in HCO3-

COMPANSATION IN ACID-BASE DISORDERS ACUTE RESPIRATORY ACIDOSIS HCO3 increases 1 mEq/L for every 10 mm Hg increase in PCO2

CHRONIC RESPIRATORY ACIDOSIS HCO3 increases 3.5 mEq/L for every 10 mm Hg increase in PCO2

ACUTE RESPIRATORY ALKALOSIS HCO3 decreases 2 mEq/L for every 10 mm Hg decrease in PCO2

CHRONIC RESPIRATORY ALKALOSIS HCO3 decreases 5 mEq/L for every 10 mm Hg decrease in PCO2

CASE #2

LABORATORY FINDINGS Glucose: 88 mg/dl BUN: 18 mg/dl Creatinine: 0.8 mg/dl Na: 136 mEq/L K: 3.0 mEq/L Cl: 96 mEq/L

Arterial Blood Gas PO2: 92 mm Hg PCO2: 36 mm Hg v HCO3: 30 mEq/L u pH: 7.54 Alkalemia

Anion Gap = 136 – (96 + 30) = 10 mEq/L Chronic Respiratory Alkalosis and Metabolic Alkalosis

CASE #2

Chronic Respiratory Alkalosis (Pregnancy) + Metabolic Alkalosis (Vomiting)

CASE #3

A 73-year-old man was sent from a hospital after being hospitalized for 3 days because of dyspnea and decreased urine output

CASE #3

The patient had a history of type 2 diabetes mellitus for 10 years

CASE #3

PHYSICAL EXAMINATION • The patient was lethargic • Skin turgor was decreased • Blood pressure: 90/60 mm Hg • Pulse rate: 100/min • •

Respiration rate: 25/min Bibasilar crackles were noted on auscultation

• Temperature: 37.80C • The patient had a urinary catheter Any comments about the diagnosis ?

CASE #3

LABORATORY FINDINGS Glucose: 142 mg/dl BUN: 89 mg/dl Creatinine: 4.9 mg/dl Na: 143 mEq/L K: 3.1 mEq/L Cl: 108 mEq/L

Arterial Blood Gas PO2: 86 mm Hg PCO2: 22 mm Hg HCO3: 14 mEq/L pH: 7.42

What is the acid-base disorder ?

CASE #3

LABORATORY FINDINGS Glucose: 142 mg/dl BUN: 89 mg/dl Creatinine: 4.9 mg/dl Na: 143 mEq/L K: 3.1 mEq/L Cl: 108 mEq/L

Arterial Blood Gas PO2: 86 mm Hg PCO2: 22 mm Hg v HCO3: 14 mEq/L v pH: 7.42 Normal

Anion Gap = 143 – (108 + 14) = 21 mEq/L

PCO2 = [(1.5 X HCO3-) + 8] + 2 PCO2 = [(1.5 X 14) + 8] = 29 mm Hg

CASE #3

LABORATORY FINDINGS Glucose: 142 mg/dl BUN: 89 mg/dl Creatinine: 4.9 mg/dl Na: 143 mEq/L K: 3.1 mEq/L Cl: 108 mEq/L

Arterial Blood Gas PO2: 86 mm Hg PCO2: 22 mm Hg v HCO3: 14 mEq/L v pH: 7.42 Normal

Anion Gap = 143 – (108 + 14) = 21 mEq/L High Anion Gap Metabolic Acidosis and Respiratory Alkalosis

CASE #3

High Anion Gap Metabolic Acidosis (Renal failure) + Respiratory Alkalosis (Sepsis)

CASE #4

A 42-year-old man was brought to the emergency department after he was found lying on the street.

CASE #4

PHYSICAL EXAMINATION • • • • • • • • •

The patient was unresponsive The pupils were minimally reactive to light Blood pressure: 120/80 mm Hg Pulse rate: 110/min Respiration rate: 28/min Temperature: 370C Bibasilar crackles were noted on auscultation Deep tendon reflexes were brisk and symmetric Plantar reflexes were normal Any comments about the diagnosis ?

CASE #4

LABORATORY FINDINGS Glucose: 110 mg/dl BUN: 30 mg/dl Creatinine: 1.5 mg/dl Na: 145 mEq/L K: 5 mEq/L Cl: 97 mEq/L

Arterial Blood Gas PO2: 90 mm Hg PCO2: 35 mm Hg HCO3: 14 mEq/L pH: 7.22

What is the acid-base disorder ?

CASE #4

LABORATORY FINDINGS Glucose: 110 mg/dl BUN: 30 mg/dl Creatinine: 1.5 mg/dl Na: 145 mEq/L K: 5 mEq/L Cl: 97 mEq/L

Arterial Blood Gas PO2: 90 mm Hg PCO2: 35 mm Hg v HCO3: 14 mEq/L v pH: 7.22 Acidemia

Anion Gap = 145 – (97+14) = 34 mEq/L High Anion Gap Metabolic Acidosis

CASE #4

LABORATORY FINDINGS Glucose: 110 mg/dl BUN: 30 mg/dl Creatinine: 1.5 mg/dl Na: 145 mEq/L K: 5 mEq/L Cl: 97 mEq/L

Arterial Blood Gas PO2: 90 mm Hg PCO2: 35 mm Hg v HCO3: 14 mEq/L v pH: 7.22 Acidemia

PCO2 = [(1.5 X HCO3-) + 8] + 2 PCO2 = [(1.5 X 14) + 8] = 29 mmHg High AG Metabolic Acidosis + Respiratory Acidosis

CASE #4

LABORATORY FINDINGS Glucose: 110 mg/dl BUN: 30 mg/dl Creatinine: 1.5 mg/dl Na: 145 mEq/L K: 5 mEq/L Cl: 97 mEq/L

Arterial Blood Gas PO2: 90 mm Hg PCO2: 35 mm Hg v HCO3: 14 mEq/L v pH: 7.22 Acidemia

Anion Gap = 145 – (97+14) = 34 mEq/L Δ AG : 34 – 12 mEq/L = 22 mEq/L

Δ HCO3 : 24 – 14 mEq/L = 10 mEq/L

CASE #4

LABORATORY FINDINGS Glucose: 110 mg/dl BUN: 30 mg/dl Creatinine: 1.5 mg/dl Na: 145 mEq/L K: 5 mEq/L Cl: 97 mEq/L

Arterial Blood Gas PO2: 90 mm Hg PCO2: 35 mm Hg v HCO3: 14 mEq/L v pH: 7.22 Acidemia

Anion Gap = 145 – (97+14) = 34 mEq/L Δ AG : 34 – 12 mEq/L = 22 mEq/L

Δ HCO3 : 24 – 14 mEq/L = 10 mEq/L

Δ AG > 2 Ö High AG metabolic acidosis Δ HCO3 and metabolic alkalosis

CASE #4

LABORATORY FINDINGS Glucose: 110 mg/dl BUN: 30 mg/dl Creatinine: 1.5 mg/dl Na: 145 mEq/L K: 5 mEq/L Cl: 97 mEq/L

Arterial Blood Gas PO2: 90 mm Hg PCO2: 35 mm Hg v HCO3: 14 mEq/L v pH: 7.22 Acidemia

High AG Metabolic Acidosis Respiratory Acidosis Metabolic Alkalosis

CASE #4

High Anion Gap Metabolic Acidosis (Ethylene glycol intoxication) + Respiratory Acidosis (Respiratory depression) + Metabolic Alkalosis (Vomiting)